Enzyme extraction process for tea

ABSTRACT

An improved process for the preparation of acid stable instant tea is disclosed. Enzymatic extraction of black tea leaf with water containing tannase and one or more cell wall digesting enzymes, such as cellulase, pectinase, hemicellulase or VISCOZYME is employed. The resulting tea extract is polished, at a selected tea solids level and temperature to improve haze. The polished extract is then made into a finished beverage or concentrated and dried in the usual manner. As a result, natural tea products are obtained which have improved acid stability, good color and good clarity.

This is a continuation application of Ser. No. 08/596,976, filed Feb. 5,1996, now abandoned.

FIELD OF THE INVENTION

The present invention relates to an improved a process for obtaininginstant tea and to the improved products thereby obtained. Inparticular, the invention relates to a method of treating black tea leafwith an enzyme cocktail including tannase and selected cell wall lysisenzymes such as cellulase, mascerase and carbohydrases for example,VISCOZYME L obtainable from NOVO Industri A/S Denmark to produce instanttea which has improved acid stability with good cold water solubility,good clarity and tea color and which has a full complement of teaflavor. The improvement is in the method of polishing the tea extract

BACKGROUND OF THE INVENTION

Enzymatic treatment of tea leaves either continuously or batchwise, forthe production of instant teas offers many benefits for the resultingconvenience beverage product. These include better acid stability,color, clarity, cold water solubility, flavor and higher yield.Continuous processing of tea leaf with enzymes is an economical methodof providing the necessary operating conditions of time, temperature,enzyme concentration and water for the enzymes to be effective. The highthroughput needed for commercial production is also accommodated bycontinuous processing with minimal complexity compared to batchoperation.

The long contact times required for enzymes to be used effectively makesbatch processing complex and requires a large capital investment inequipment to provide the residence time. Continuous, plug flow treatmentreduces the amount and complexity of equipment needed to treat tea leafwith enzymes and allows for easy integration to downstream continuousextraction process equipment. Consistent, reproducible results is afurther benefit of continuous treatment.

Black tea is usually prepared by subjecting freshly picked tea leaves toa series of processing conditions including the withering and rolling offreshly harvested leaves, followed by a fermentation step (enzymaticoxidation) during which much of the characteristic color, flavor andaroma of black tea are developed. The fermentation is halted after asuitable period of time by "firing" or drying the tea at temperaturesranging from about 65° C. to about 100° C. to inactivate the enzymescausing the fermentation. This completes the development of the flavorand color of the tea product. The extent of fermentation varies, incommercial practice, from black to various gradations between green andblack. Partially fermented teas are known as "oolong" teas. Green teasare made by firing green tea before fermentation has taken place. Green,oolong, and black tea each provide a beverage having distinctive flavorand color characteristics.

When conventional teas are extracted with cold water for short periodsof time (less than 15 minutes), the tea beverage produced has a lowconcentration of extractable tea solids, a very light color and almostno tea-like taste. Water at temperatures of about 100° C. is customarilyemployed by the prior art to obtain a satisfactory beverage.

Various procedures are known in the art for making cold water solubleinstant tea powders by solubilizing tea cream obtained from black teaextracts, e.g., Herz, U.S. Pat. No. 2,831,772; Perech, U.S. Pat. No.2,863,775. While each of these processes are successful to varyingdegrees in producing a cold water soluble instant tea powder, each hasdisadvantages. Most fail to provide a tea powder which, onreconstitution, gives a beverage having a natural flavor and color.

Sanderson et al. U.S. Pat. Nos. 3,812,266 and 4,051,264 employ tannasewith green tea.

Tsai. U.S. Pat. No. 4,639,375 treats tea with a combination of tannaseand one or more cell wall lysis enzymes but only, prior to extraction.

There is a substantial body of literature on the role of enzymes in teamanufacture, which has been summarized in two review articles, Sanderson& Coggon, ACS Symposium Series, No. 47, pp. 12-26 (1977); and Roberts,J. Sci. Food Agric., 3, 193-8 (1952).

U.K. Patent 1,249,932, relates to a process for the solubilization oftea cream and to the preparation of water-soluble tea concentrates bythe use of an appropriate enzyme, especially tannase.

U.K. Patent 1,380,135, describes the preparation of a cold water solubleinstant tea powder containing solubilized tea cream. The process of the'135 specification involves either separating cold water-insoluble teasolids from the hot water extracted tea and treating them with tannaseor treating the hot water extract of tea with tannase withoutseparation.

U.K. Patent 1,413,351, relates to a process in which unfermented (green)tea is contacted with tannase and is subsequently converted to blacktea.

U.K. Patent 1,546,508, relates to a method of treating fresh green tealeaf with tannase.

U.S. Pat. No. 5,445,836 relates to a process for producing tea extractwith reduced haze under refrigeration using tannase and glucose oxidaseto treat decreamed tea extract.

U.S. Pat. No. 3,959,497, relates to enzymatic solubilization of teacream by treating tea extract or tea cream with enzymes.

In the prior art tea polishing is accomplished in part by centrifugationof the tea extract. It was not known that the percent of tea solids inthe extract was critical in obtaining a reduced haze final product.

It is an object of this invention to provide an enzymatic extraction forthe treatment of black tea leaf which produces a high quality naturalproduct with good acid stability having haze values of a final black teabeverage of less tan 50 as measured by a Hunter Colorimeter.

It is another object of this invention to provide an improved continuousprocess for enzymatic extraction of black tea leaf which produces aproduct having better acid stability, greater cold water solubility,better color and better clarity than conventional black tea extracts.

Yet another object is to overcome or substantially eliminate the manyproblems of the art.

These and other objects of the invention will be evident from thefollowing disclosure.

SUMMARY OF THE INVENTION

Black tea is obtained in the usual way and employed in the instantprocess. Black tea leaf can be used as received.

An enzyme cocktail containing tannase and selected cell wall lysisenzymes is prepared. It has been found that the pH of the enzymecocktail which includes tannase in combination with the other enzymes,is critical to obtain high tannase activity to result in a high yield ofgallic acid. It is believed that the gallic acid content of the instanttea product is, in part, indicative of the degree of solubility, withhigher levels of gallic acid correlating to better solubility.

While not wishing to be bound by theory, it is nevertheless theorizedthat treatment of the tea leaves with the tannase and cell walldigesting enzymes leads to a soluble tea product with a uniquebiopolymer profile. Tannase results in increased gallic acid or gallicacid salt levels from modification of polyphenolic type biopolymers suchas theaflavins and thearubigins. The cell wall digesting enzymes releaseand modify plant cell wall biopolymers, thus creating products whichcontribute to flavor and acid stability.

While it is known that certain tea polyphenols precipitate selectedproteins under acidic conditions below the isoelectric point of theproteins, the modification of the proteinaceous biopolymers present intea leaves to a favorable profile as disclosed herein improvessolubility.

The enzymes are fed to a black tea/water slurry in the extractor at lowtemperature to obtain a tea extract slurry. The enzymes can be combinedinto a cocktail with appropriate pH adjustment or can be fed to theextractor individually to limit the contact time between the enzymes.The tea extract slurry containing the enzymes is hot extracted tocomplete the extraction process and the tea leaf is separated from thetea extract. The tea extract is then pasteurized. This heat treatmentdeactivates the enzyme cocktail.

The separated or decanted tea extract may then be stripped, if desired,to collect additional aroma.

The optionally stripped extract is then cooled and polished bycentrifugation or other clarification methods such as filtration or thelike. It has been found that during centrifugal polishing a selected teasolids content and a particular temperature are essential to produce aproduct of the desired color, clarity and acid stability.

After polishing the extract may then be concentrated and dried in theusual manner to a powdered instant tea or the extract can also beemployed as a liquid or syrup when preparing tea based beverages.

About 5 to 20 parts and preferably 5 to 8 parts by weight of water basedon the weight of tea leaf is heated to between about 70° F. and 145° F.,preferably 120° F. to 140° F. The water is added to the tea leaf and anenzyme mixture consisting of any combination of tannase with thefollowing: Carbohydrases such as cellulose, pectinase and mascerase aremetered continuously into the extractor. The extractor can be jacketedor insulated to aid in temperature control. The flow of tea leaf, waterand enzymes through the extractor is preferably co-current. The length,diameter and flow rates of the system are such that they provide aminimum contact time of at least 20 minutes, preferably at least 60minutes. The maximum is about 2 to 5 hours or more, depending upon thedegree of extraction desired balanced against economics.

The resulting slurry can be separated into extracted tea leaf andextract or be sent on for further batch or continuous extraction. Theextract is then optionally aroma stripped by conventional means andadjusted to the desired solids level, cooled and centrifuged to removeinsoluble material. The extract is optionally batched into a finishedbeverage, or if desired can be concentrated and/or dried, for examplespray dried.

The color and clarity of the resulting product is significantly improvedif the centrifugation is done on an extract of about 4.0 wt. % to 10 wt.% tea solids.

There are several product advantages to the improved instant teaprocess. Acid stability is one advantage. This refers to the tendencyfor solids to precipitate or floc out of solution, especially in acidsystems. Other benefits are improved color, clarity, cold watersolubility, flavor, and extraction yield.

Acid stability as referred to herein may be measured by two differentmethods. Method 1 is employed to determine the acid stability of afinished product prepared from tea powder, flavor, citric acid, waterand optionally sweetener, e.g., sugar aspartame and the like. The wateremployed preferably has a hardness of 170 ppm. The finished product isvisually inspected for precipitated floc. Color and clarity are measuredusing a Hunter Colorimeter with a 4 cm sample cell. A haze value of lessthan about 50 is acceptable. The product is then stored at about 40° F.for 48 hours. At the end of this period the product is again observedfor flocculated particles or precipitation and again measured for colorand clarity. The product is acid stable if there is no floc orprecipitation and there is no substantial change in haze value and thusthe haze still must remain less than about 50. The tea extract used toprepare the powder is, in like manner, acid stable. The HunterColorimeter employed is a Hunter Lab Color Quest System with a HunterLab DP-9000 data module.

In method 2 an instant tea sample is made up to a product strength of0.17% w/v in water, in a buffer solution at pH 2.5. To pass the visualobservations the sample should remain clear without any sign ofprecipitate formation when dissolved in pH 2.5 buffer after 24 hours.

Along with visual observations, readings for haze and color using aHunter Colorimeter are also recorded.

Equipment

Hunter Colorimeter with 4 cm or 5 cm cells;

Tapered graduated tubes--10 ml.

Method 2

Phosphate/Citric Acid Buffers

I. Stock Solutions.

A. 0.4M di-Sodium hydrogen orthophosphate is prepared in deionizedwater.

B. 0.2M Citric acid is prepared in deionized water.

II. Dilute Working Buffer Solutions.

pH 2.50 Buffer. 85 ml of phosphate solution A is mixed with

915 ml citric solution B.

Procedure

0.17 g of instant tea powder is added to a conical flask. 50 ml ofdeionized water is then added to the flask and the flask is shaken todissolve the tea powder. 50 ml of pH 2.50 buffer solution is added tothe flask, the contents are mixed and then without undue delay the hazeand color (L values) are measured. After allowing the extract to standovernight, the extract in the graduated tube is examined and any signsof precipitate formation either suspended or settled is noted. Furtherhaze and color measurements are performed to confirm a good batch ofproduct.

To pass the visual observations the sample should remain clear withoutany sign of precipitate formation when dissolved in pH 2.5 buffer after24 hours.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Aroma Stripping

100 lb. of tea leaf is fed into a Hopper. The leaf is then fed into anAroma Stripper. The leaf in the Stripper is then steam stripped tocollect selected fractions of tea volatiles or aroma. The steam strippedaroma leaves the vessel and is condensed and collected. Other methods ofaroma collection are also acceptable. After stripping, the tea leaf ismetered into the enzyme extractor.

Enzyme Preparation

The enzyme cocktail is prepared by mixing selected cell wall digestingenzymes together with enzyme stabilizing agents such as sorbitol and thelike in water. Tannase may also be prepared by adding the enzyme towater first but the tannase may also be added as a dry powder. Theenzymes are mixed together and their pH is adjusted to about 4 to 10 andpreferably 5.5 or above, more preferably about 6.0 or above so long asthe enzyme is not denatured. The cell wall digesting enzyme mixturepreferably has its pH adjusted prior to dissolving or adding the tannaseinto the enzyme cocktail. It is also possible to introduce the enzymesseparately into the extractor.

The enzyme batch contains about 340 grams of the cell wall digestingenzymes and contains about 3.8 grams of the tannase on the carrier.

The enzyme cocktail is maintained at a temperature of about 35° F. to55° F. and is added into the extractor at a rate of about 3.4 g/minute.

The addition of the enzyme solution to the enzyme extractor affects thecarbohydrate composition, the gallic acid concentration, the acidstability and the cold water solubility and yield. The preferredconditions of the extraction are as follows:

Temperature in the extractor 70° F. to 145° F. and preferably about 120°F. to 140° F.

Enzyme Feed Rate target 3.4 gm./min.

Leaf Feed Rate target 60 lbs./hr.

Water Feed Rate 5.0 to 8.0 lb/min.

Enzyme Extraction Operation

The tea leaf is fed to the enzyme extractor from the aroma strippertogether with fresh water and enzyme solution. All three components flowco-currently through the extractor. The extractor is preferablytemperature controlled. This is maintained via hot water jacketing orthe like.

The enzyme extractor preferably provides about 20 minutes to about 5hours or more of residence time for the enzyme solution to be in contactwith the leaf. Temperature control is important to maximize the effectof the enzymes.

Operating Parameters for the Enzyme Extractor

The following table highlights the preferred operating parameters:

    ______________________________________    Operating Parameter                    Specification    ______________________________________    Leaf Feed Rate  60 lb/hr    Feedwater Rate  0.6 to 0.95 gallons/min.    Enzyme Feed Rate                    3.4 gm/min    Slurry Temp. in Troughs                    120-140° F.    ______________________________________

High Temperature Extraction

Following the enzyme extraction step, the leaf slurry is preferably fedinto a high temperature extractor at a temperature of about 180° F. to200° F., preferably 190° F. This completes the extraction of the leaf.The ratio of leaf to water in this extraction is about 4 parts to 10parts water to 1 part leaf.

Pasteurization

Decanted extract from the hot extraction step is pumped at about 2% to5% tea solids to the Pasteurizer. Pasteurization is accomplished byraising the temperature of the extract to a minimum of about 190° F. Thehot extract is then held for about one to ten minutes residence time todestroy any microorganisms that might be present in the extract. Thepasteurization step also denatures the enzymes and stops their activity.

The pasteurized extract is then again stripped of aroma if desired andconcentrated to the appropriate level for centrifugal polishing.

Polisher Operation

The feed solids concentration and temperature of the extract beingpolished has been determined to be critical to achieving good qualityproduct. The concentrated pasteurized extract is best polished at a teasolids concentration of about 4% to 10%. If the solids concentration istoo high, the result will be light color and high polishing loss. If thesolids concentration is too low, the result will be high haze.

The extract temperature should be about 120° F. or less, preferablyabout 55° F. to 70° F. The extract is fed to a centrifuge where it isspun for nominally 2 minutes at approximately 8,000 times gravity. Thesludge is disposed of and the polished extract retained for formulatinginto finished beverage, concentration and/or drying. Higher temperatureswill result in a final product that is hazy. It can also allowmicrobiological spoilage. Lower temperatures will result in lightproduct and high polishing losses.

The Polisher Operation mainly affects two parameters; color and haze.

Evaporation

The polished extract may then be concentrated by evaporation or othermethods if desired.

Aroma Addition

Tea concentrate from the evaporation process is collected and dependingupon the product being produced, aroma or volatiles previously collectedmay be added if desired.

Drying

The concentrated extract is then dried if a tea powder is beingproduced. The extract can also be diluted and used directly if desiredin a ready to drink beverage.

There are many variables that affect product quality and yield at thedrying step. Drying processes are well known in the art.

In a preferred process of this invention, black tea leaf is mixed withan enzyme cocktail at a weight ratio of from about 0.005 to 0.010 partsof enzyme to 1 parts of the leaf preferably 0.007 to 0.008 parts ofenzyme per part of tea leaf. The enzyme solution contains tannase andone or more cell wall lysis enzymes. Preferably, the enzyme solutioncontains from about 0.5 to 10 units of tannase activity per gram ofblack tea, and from about 2.5 to 5.0 NCU of cellulase, and about 0.33 to0.66 FBG of carbohydrase per gram of black tea. The tea is extractedwith the enzymes at a temperature of from about 70° F. to about 145° F.for from 20 minutes to 5 hours or more. The enzymes are inactivated byheating to a temperature greater than about 150° F. and preferably 190°F. or above and the tea is then ready for further processing inaccordance with the invention.

Enzyme Solution

By "cell wall-digesting enzyme" herein is meant an enzyme which breaksdown one or more tea cell wall constituents to simpler materials andthus reduces the structural integrity or increases the permeability ofthe cell wall. Plant cell walls are composed primarily of cellulose, butcontain lesser amounts of proteins, hemicellulose, pectins, and lipids.Accordingly, cell wall digestive enzymes include carbohydrase such ascellulose, hemicellulase, pectinase and dextranase; protease, lysozymeand lipases. For example, Novo Industries U.S. Pat. Nos. 4,478,939 and4,483,876 describe SPS-ase activity.

The tannase which is used in this invention is known to hydrolyzegalloyl esters. The enzyme is an elaboration product of the growth ofcertain molds belonging to the genera Aspergillus and Penicillium.Aspergillus flavus grown on a medium containing tannic acid as a solecarbon source provides tannase in substantial amounts. Two otherspecific strains of microorganisms known to produce substantialquantities of tannase are Aspergillus oryzae, ATCC No. 9362, andAspergillus niger, ATCC No. 16888. One suitable preparation of tannaseenzyme is available commercially from the Enzyme DevelopmentCorporation. Yet another is available from Kikkoman. The other cell walldigesting enzymes, such as cellulase, papain, pectinase, andhemicellulase can be obtained from similar commercial enzyme sources.One example of the measurement of tannase activity is given below.

Tannic acid is hydrolyzed in the presence of tannase to gallic acid anda sugar moiety. The hydrolysis of tannic acid results in a reduction ofUV absorbance at 310 nm. Tannase activity is therefore determined fromthe change in absorbance and is defined as the amount of enzyme whichhydrolyses 1 micromole of ester bond in tannic acid per minute under theconditions described below.

Reagents and Solutions

(1) Citrate Buffer (0.05 M, pH 5.5)

Dissolve 9.6 grams of anhydrous citric acid in 800 ml of water. AdjustpH with NaOH (50%) to 5.5 and dilute to 1000 ml with deionized water.

(2) Cell Wall Digesting Enzyme Solution (33.0%)

This solution is a mixture of and CELLUCLAST that have been blended in aratio of 2:1. The mixture serves as the solvent, stabilizer and blankfor the tannase analysis. The solution is prepared on a W/V basis withdeionized water. The pH is adjusted with sodium hydroxide to 5.5.

(3) Substrate Solution (Tannic Acid, 0.350% WN)

The substrate is prepared just before use by dissolving 175 mg of tannicacid in citrate buffer (1) which is then made up to a volume of 50 mlusing a volumetric flask.

(4) Ethanol Solution (90%)

100 ml of deionized water is added to a 1000 ml volumetric and thevolume is brought to 1000 ml with ethanol.

(5) Tannase Solution (Approx. 2.6-29 units/ml.)

The tannase solution is prepared by dissolving 0.1000 grams of tannasein the cell wall digesting enzyme solution(2) WN to produce a solutionthat contains 1.000 mg/ml tannase. 1.0 ml of tannase solution is dilutedwith 18 ml of citrate buffer (1). This brings the tannase into therequired activity range for U.V. analysis The blank is prepared in thesame way by mixing 1.0 ml of Novoferm 91 (2) solution with 18 ml ofcitrate buffer (1).

Stability of Solutions: Citrate buffer (1) when stored at 4° C. isstable as long as no microbial action occurs. The cell wall digestingenzyme solution (2) and substrate solution (3) must be freshly preparedand protected from light. Ethanol solution (4) may be stored at roomtemperature. Enzyme solution (5) may be stored for several hours atabout 0°-4° C. after preparation.

Procedure

A. The substrate solution (3) is transferred to a flask and warmed in awater bath at 30° C. for 15 minutes before starting the enzyme reaction.

B. 1.0 ml aliquots of enzyme solution (5) are transferred into testtubes (10 ml). For blank test samples the cell wall digesting enzymeblank solution as specified in (2) is used. All test tubes are warmed ina water bath at 30° C. for 5 minutes before starting the enzymereaction.

C. The test/reaction is begun by adding 4.0 ml) of substrate solution(3) to each test tube (at 30 second intervals) and incubated for 15minutes at 30° C.

D. The reaction is quenched in flasks for each test sample by addingethanol solution (4) to each flask. At the end of the reaction time,which should be 15 minutes for each test sample, 952 ul of sample istransferred to the ethanol stop solution and mixed thoroughly. Thesample is diluted to volume with additional ethanol solution (4) andmixed.

E. The absorbance of each solution is measured at 310 nm using water asa reference.

Calculations

(1) The absorbance measurements that were taken for the samples andblanks are averaged.

(2) Tannase activity may then be calculated from the following equation:

    Tannase Activity (Units/gram)=ΔA*150670

The cell wall digesting enzymes may be cellulase such as CELLUCLAST 1.5Lobtainable from Novo Industries. This material is prepared byfermentation of a selected strain of Trichoderma reesei. This cellulasecatalyzes the breakdown of cellulose into glucose, cellobiose and higherglucose polymers. CELLUCLAST 1.5 L has 1,500 NCU/g.

One Novo Cellulase Unit (NCU) is the amount of enzyme which, understandard conditions,degrades CMC to reducing carbohydrates with areduction power corresponding to 1 μmol glucose per minute.

    ______________________________________    Standard Conditions    ______________________________________    Substrate      CMC (Hercules 7 LFD)    Temperature    40° C.    pH             4.8    Reaction time  20 minutes    ______________________________________

Another cell wall digesting enzyme is VISCOZYME L obtainable from Novo.VISCOZYME 120 L is a multi-enzyme complex containing a wide range ofcarbohydrases including arabinase, cellulase, β-glucanase, hemicellulaseand xylanase. The enzyme also has activity against the branched pectinlike substances found in the soy bean cell walls.

The enzyme preparation is produced from a selected strain of theAspergillus group. The product has an enzyme activity of 120 FBG/ml.(Fungal β Gluconase). The analytical method is available from Novo.

It is found that the pH of the mixed enzyme solution is very importantin obtaining the highest yields of gallic acid as a result of hightannase activity. The combination of cell wall digesting enzymes has apH of about 4.0 to 5.0 and this is adjusted up to 10, preferably to 5.0to 6.5 to provide higher tannase activity.

In addition to the pH of the enzyme treating solution being extremelyimportant it is also found that the polishing/cooling step is veryimportant. The amount of solids in the extract should be from 3.5% to20%, preferably from 4% to 10% to achieve good color and clarity.

The temperature to which the extract is cooled is also important. Thetemperature should be less than about 120° F. and preferably about 55°F. to 70° F.

Polishing/Examples

A series of experiments are run to determine the effect of solids level,feeding, and polishing on the haze of the finished powder.

The primary objective of the experiments was to determine ifconsistently "low" haze levels (i.e., <30 haze) could be achieved byincreasing the solids level of the extract feeding the polishers. Inaddition to haze effects, L-value, A-value, and polishing loss datareported below were all tracked.

Table 1 below summarizes the data that was gathered from this series ofruns.

Details of Experimentation

For each run that was made during this experimental series, theextracted solids were split equally. This was done to ensure that anydifferences in result would be due to polishing only and not due to anydifferences in extraction.

A control was always run which was native solids with no concentration.The other part of the batch was concentrated up to the solids level atwhich the experiment was run. The batches were then polished separatelybut at the same polishing conditions (given above), concentrated, andspray dried separately. All of the attached color and haze data is onfinal powder.

Color and haze was measured at 0.35% solids in synthetic hard water at60° F. using a 5 cm. Hunter cell.

                  TABLE 1    ______________________________________    Polishing Solids Experiments    Polishing      Spray Dried Powder                                  Polishing    Exp. #  Solids (%) L      A      H    Loss (%)    ______________________________________    1       3.87       32.4   26.5   32.2    2       3.30       31.8   29.4   35.4    3       3.16       24.2   28.2   49.0 7.9    4       2.97       20.9   26.7   46.9    5       2.80       19.1   25.1   55.7 6.7    6       3.02       25.1   27.3   53.8    7       2.80       18.8   25.8   62.8 7.1    8       7.07       33.7   29.8   9.4  16.3    9       10.70      34.1   31.0   16.2 14.5    10      4.59       28.8   31.5   27.8 16.0    11      2.89       26.1   31.7   38.0 6.6    12      3.60       22.4   26.8   50.5 15.8    13      4.25       27.8   29.2   29.4 15.8    14      3.40       25.5   26.8   38.3 14.9    15      4.70       30.3   29.2   22.0 16.5    ______________________________________     All sample colors were measured at 0.35% solids at 60° F. in     synthetic hard water using a 5 cm. Hunter cell.

The results indicate that by increasing the solids level of the extractfeeding the polishers, significant reductions in haze are achieved. Atsolids levels typical of decanted extract with no concentration (i.e.,2.7-3.2%), haze levels varied from 30 to 63. At solids levels after someconcentration is done (i.e., >4%), haze levels ranged from 10 to 29.Polishing temperature was maintained at 60° F. for all runs and feedrate was 550 mls./min. for all runs. Prior to this series ofexperiments, polishing was carried out on native extract at it comes offthe decanter with no further concentration.

In addition to the haze shift that occurs when polishing solids areincreased, there is a shift in beverage color as well (L-value). Whilethe L-value shift is quite significant at solids levels of 7% and above,at the 4.5% level it would still be within an acceptable L-value range.

It should be noted that the inverse relationship between haze andL-value seen here is a typical phenomenon which occurs routinely innon-enzymatically processed teas. Products that are high in haze and arere-polished to bring the haze down usually also undergoes an upwardshift in L-value (i.e., lighter).

With regard to polishing losses, these also are significantly higher atthe higher solids level (i.e., 6-8% at solids <3.3% vs. 14-16% atsolids >3.3%). This is consistent with the L-value and haze shifts aswell as with non-enzymatically processed teas.

The final parameter, "A-value" (redness), shows the least effect fromvarying polishing solids, but here too, the apparent shift is consistentwith expected values. A lowering of the haze typically results in anincrease in "redness" of the beverage (i.e., higher A-value).

1) Significant reductions in haze can be achieved by slightly increasingthe solids level at polishing from 3.0% to 4.5% or higher.

2) By a combination of reduced water to leaf ratio and vacuum strippingbefore polishing, it is estimated that polisher feed solids level of4.5% could be achieved. This would be sufficient to produce the desiredreduction in haze without increasing the L-value to an unacceptablelevel.

3) Polishing losses are significantly higher when polishing at thehigher solids level.

Although the invention has been described in detail with respect topreferred embodiments thereof, variations and modifications will bereadily apparent to those skilled in the art without departing from thespirit and scope of the invention as set forth in the claims.

What is claimed is:
 1. A process for producing a soluble black teaproduct by enzymatic extraction, said product upon being reconstitutedinto an acidic beverage remaining stable, comprising the steps of:(1)co-extracting fermented black tea leaf with water and an enzymecombination comprising tannase and one or more cell wall-digestingenzymes which break down one or more tea cell wall constituents tosimpler materials; (2) inactivating the enzymes by heating; and (3)clarifying the extract at a % tea solids of 3.5 to 20% and a temperatureof less than 120° F.; whereby said acidic beverage remainsflocculate-free for 48 hours at 40° F. and has a haze value of less than50.
 2. A process according to claim 1, wherein the extraction takesplace for from about 20 minutes to about 5 hours.
 3. A process accordingto claim 1, wherein the enzymes are inactivated by heating to atemperature of at least 150° F.
 4. A process according to claim 1,wherein the cell wall-digesting enzyme is a member selected from thegroup consisting of cellulase, hemicellulase, pectinase, dextranase,lysozyme and lipase, and mixtures thereof.
 5. A process according toclaim 1, wherein the enzyme solution contains from about 0.5 to about 10units of tannase per gram of tea leaf, wherein one unit is the amount ofenzyme which hydrolyses one micromole of ester bond in 0.35% tannic acidin 0.1 m. citrate buffer having a pH of 5.5 in one minute at 30° C.
 6. Aprocess according to claim 1, wherein said extract is dried to form apowder.
 7. A process according to claim 1, wherein said extract isreconstituted to form an acidic beverage.
 8. A process according toclaim 1, wherein said extract is concentrated to form a syrup.
 9. Aprocess for reducing the haze in spray dried tea obtained by enzymeextraction comprising adjusting the solids content of said extract toabout 3.5% to 10% prior to polishing and polishing at a temperature ofless than 120° F.
 10. A continuous process for producing a soluble blacktea product by enzymatic extraction, said product upon beingreconstituted into an acidic beverage remaining stable, comprising thesteps of:(1) continuously co-extracting fermented black tea leaf withwater and an enzyme combination comprising tannase and one or more cellwall-digesting enzymes which break down one or more tea cell wallconstituents to simpler materials; (2) inactivating the enzymes byheating; and (3) clarifying the extract at a % tea solids of 3.5 to 20%and a temperature of less than 120° F.; whereby said acidic beverageremains flocculate-free for 48 hours at 40° F. and has a haze value ofless than
 50. 11. A tea product comprising tea solids prepared fromblack tea leaf which has been extracted by aqueous treatment with anenzyme cocktail containing tannase and at least one cell wall-digestingenzyme at an initial enzyme pH of 5.0 to 6.5 and polished at a solidsconcentration of 4.0 to 10%, and a temperature of less than 120° F. andwhich, when formulated into a final product having a percent tea solidsconcentration of about 0.05% to 1.0%, does not form haze for 48 hours at40° F. as measured by a Hunter colorimeter and remains free ofprecipitate.
 12. A continuous process for producing a soluble black teaproduct by enzymatic extraction, said product upon being reconstitutedinto an acidic beverage remaining stable, comprising the steps of:(1)continuously co-extracting fermented black tea leaf with water and anenzyme combination comprising tannase and one or more cellwall-digesting enzymes which break down one or more tea cell wallconstituents to simpler materials; (2) inactivating the enzymes byheating; and (3) clarifying the extract at a % tea solids of 3.5 to 20%and a temperature of less than 120° F.; whereby said acidic beverageremains flocculate-free for 48 hours at 40° F. and has a haze value ofless than 50.